350 93. LEMXACE^. — 94. potamogetoxacej:. 
Order XCni. LEiLN'ACE^. 
Fl. monoecious, 2, in a spath, but without a spadix. Perianth 
0. Stam. 1—2, distinct. Ovary l-celled. Style short. Stignia 
simple. Fr. bladdery, not bmsting. Seeds with a coriaceous 
ribbed testa. — Floating, leaflike, small ; no distinction of st. or 
leaf. Fl. very minute. 
1. Lemna. Spath membranous, umshaped. Stam. 1 — 2. 
Anth. 2-ceUed, didymous (cells bilocular?). — Fl. from just 
below the edge of the frond. — Increasing chiefly by buds. 
1. Lem'xa Lmn. Duckweed. 
1. Z. trisurca(L.) : frondsthm pellucid elliptic-/anceo/«fetailed 
at one end serrate at the other, roots solitaiy. — E. B. 926. H. 
vii. 15. — Fronds half an in. long, proliferous at right angles. 
"Filaments recurved, filiform. " Schleid. Plants truly annual, 
producing buds which siu'vive the winter as in the other species. 
— On and in stagnant water. A. VI. E. S. I. 
2. L. minor (L.) ; fronds obovate compressed opaque, roots 
solitary blunt. — E.B. 1095. R. vii. 14. — Fronds 1 — 2 lines lonw, 
nearly flat beneath, of a compact texture. Filaments recm-ved, 
filifoi-m. — On stagnant water. A. YI. YTL. E. S. I. 
3. L. jJolyrrMzn (L.) ; fronds roundish-ohovate compressed, 
roots many clustered acute. — E. B. 2458. R. ^^i. 15. Spirodela 
Schleid., Endl. — Fronds half an in. long, green above, purple 
beneath. "Filaments nairowed below." Schleid. Fl. have hot 
been seen in Britain. — On water. A. E. S. I. 
4. L. gib'ha (L.) ; fronds obovate nearly flat above hemispheri- 
cal and spongy beneath, roots solitary blunt.— Z^. B. 1233. R. 
vii. 14. Telmatophace Schleid., Endl. — Fronds 1 — 2 lines long, 
remarkably gibbous and cellular beneath. " Filaments recm-ved, 
dilated in the middle." Schleid. See an excellent account of the 
germination of this plant, bvMr.WUson, mBot.Misc. i. 145. t.42. 
—On stagnant water. A.'VI.— YIII. E. S. I. 
Order XCIY. POTAMOGETOTfACEJE. 
Fl. perfect or imperfect. Perianth inferior, 4-parted, or 0. 
Stam. free, 1, 2 or 4. Ovaries 4, distinct, each with 1 ovule 
and 1 sessile stigma. Fr. a drupe inclosing a hard nut, or a dry 
nut, not bursting, 1-seeded. Albumen 0. Embryo with a thin 
skin having a lateiul cleft. 
1. Potamogeton. Fl. perfect. Perianth 4-parted. Anth. 
4, sessile, opposite to the di\"isions of the perianth. Ovarie.'j 
4. Styles 0. Drupes 4, sessile. — Fl. sessile, spiked. 
